Currently there exists a variety of mutants of SV4O which display a complicated range of RNA transport phenotypes. Although many of these mutants perturn RNA splice functions and often do not transport DNA,k no clear relationship has been observed to exist between splicing andtransport as other mutants are known to transport unspliced RNA. I propose to further investigate the relationship between RNA splicing and transport. My specific aims are: 1) to determine, by genetic manipulation, the important control elements that regulate the transcription of SV40genes. 2) To construct,k in vitro, a series of well-defined deletion, insertion, and rearrangement mutants involving putative control regions and may affect the splicing and transport process of SV40 transcripts. 3) To determine the in vivo transcriptional phenotypes of the above mutants and establish how these genetic perturbations affet splicing, transport, and translation of the expressed RNAs. 4) To test the hypothesis that nuclei actively retain nuclear RNA and define what distinguishes nuclear from cytoplasmic RNA. 5) To dissect the subnuclear localization of modifictions undergone by SV40 RNA during the process of splicing and transport. 6) To establish the involvement of the nuclear pore complex and the nuclear matrix in the splicing and transport of SV40 RNA and to establish an in vitro transport system.